An irregularity in a pulsar part of a binary system observed for the first time

An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes the first observation of an irregularity in the rotation period of a pulsar, a phenomenon called glitch, in a binary system. A team of scientists from the Middle East Technical University and Baskent University, both in Ankara, Turkey, used data collected from observations of the Swift, XMM-Newton and Chandra space telescopes conducted over two years to identify glitches in the pulsar SXP 1062.

The image of the pulsar SXP 1062 shows that is still surrounded by the remnants of the supernova that created it. In these cases, combining observations made with various space and ground-based telescopes at different electromagnetic frequencies allow to obtain many different details that provide an overall portrait that’s much more useful than what any single instrument could create.

The false-color iamge of the pulsar SXP 1062 (ESA / XMM-Newton / L. Oskinova, University of Potsdam, Germany / M. Guerrero, Instituto de Astrofisica de Andalucia, Spain (X-ray); Cerro Tololo Inter-American Observatory / R. Gruendl & YH Chu, University of Illinois at Urbana-Champaign, USA (optical)) combines X-rays in blue and optical frequency data with the signature of oxygen in green and that of hydrogen in red.

The pulsar SXP 1062 is about 200,000 light-years away from Earth, in the Small Magellanic Cloud, one of the Milky Way’s satellite dwarf galaxies. It’s part of a binary system and this makes it special because glitches are normally detected in isolated pulsars but so far such a phenomenon was never detected in a pulsar in a binary system.

According to the authors of this research, the companion star of SXP 1062 contributes to the glitches with its gravitational influence along with the supernova remnants, which are being attracted by the pulsar. When those materials fall on it, they cause its accretion, which in this case is a violent process.

The researchers think that the remnants and the companion star exert on the pulsar SXP 1062 forces that at some point become unsustainable, causing rapid changes in its internal structure, which transfers momentum to the surface crust. This causes a very rapid change in the pulsar’s rotation, namely the glitch.

The characteristics of this phenomenon observed in SXP 1062 are different from those observed in isolated pulsars and this suggests that the interior of neutron stars in binary systems may be different from that of isolated neutron stars. To understand it better, this research will continue using NASA’s Neutron Star Interactive Composition Explorer (NICER) instrument, sent in June 2017 to the International Space Station exactly to study neutron stars.